3vdc low voltage circuit - Page 2 - Electronic Circuits Projects Diagrams Free

b_reagle · 9th August 2008, 05:10 PM

When voltage drops to 4.8 (as suggested), then blinking LED will blink. I was informed that the batteries would start at 6vdc and then normally operate at 4 vdc. I have not done my research to comfirm this. I am not sure if LM139 is the way I want to go. There is alot of unused gates.(room, power, and size are issues) Am I getting closer with this...?

b_reagle · 9th August 2008, 05:21 PM

Whoops, I mean like this:

Mikebits · 9th August 2008, 10:58 PM

Quote:

Originally Posted by Roff

If he does the things that I have highlighted in red, the LED will be on until the voltage drops below Vref. I don't think that's what he wants. Of course, he really wants a flasher anyway, so an LED on the comparator output ain't gonna work anyway.

Oops, your right. Now that is just embarrassing

b_reagle · 10th August 2008, 12:57 AM

What about like this?

Mikebits · 10th August 2008, 01:23 AM

After my last blunder, I am somewhat afraid to give out advice, but just one comment.
For U1, from the part number you listed, the device has an open drain output which means it needs a pull up and is an active low out.

b_reagle · 10th August 2008, 01:57 AM

Then would this be correct? or closer? or just plain wrong?

kchriste · 10th August 2008, 02:31 AM

That would work, but this way is simpler and uses WAY less idle current. I have kept the resistor in series with the LED in case you will be using a regular LED, but flashing LEDs usually don't need a resistor:

b_reagle · 10th August 2008, 02:44 AM

Thanks for the help kchriste. Is this the simpliest(cheapest) way of doing this?

AllVol · 10th August 2008, 02:46 AM

Quote:

Originally Posted by Roff

If he does the things that I have highlighted in red, the LED will be on until the voltage drops below Vref. I don't think that's what he wants. Of course, he really wants a flasher anyway, so an LED on the comparator output ain't gonna work anyway.

Roff's right (say that three times after two martinis).

Attachment after Paisley

Mikebits · 10th August 2008, 02:55 AM

Did you read the follow on post, or just rubbing it in...

b_reagle · 10th August 2008, 03:02 AM

So Allvot, you say use a comparator instead of voltage reglator, or are you really just rubbing it in.LOL.

Mikebits · 10th August 2008, 03:14 AM

Quote:

Originally Posted by b_reagle

So Allvot, you say use a comparator instead of voltage reglator, or are you really just rubbing it in.LOL.

Not to rub it in, but you mean voltage detector right?

Kchriste latest plan looks the way to go IMHO.

I am going to crawl back underneath my keyboard now

b_reagle · 10th August 2008, 03:19 AM

Right voltage detector. Thanks again for your help.

kchriste · 10th August 2008, 03:29 AM

Quote:

Originally Posted by b_reagle

Thanks for the help kchriste. Is this the simpliest(cheapest) way of doing this?

It is the simplest, but not necessarily the cheapest if you have zeners and opamps in your junk box. If you need to buy the parts anyway, then my way will work out the best for you. The problem with the opamp/zener route, is that you'll have a higher current draw off the batteries and they won't last as long. Those low voltage detector circuits draw less than 3uA and you'll be hard pressed to build anything with opamps and zeners that draws less than 1000uA.

b_reagle · 10th August 2008, 03:33 AM

Good. That is a very cool part indeed. I never knew they existed. Now on the the next puzzle... Thanks again.

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10th August 2008, 01:23 AM	(permalink)
Mikebits	After my last blunder, I am somewhat afraid to give out advice, but just one comment. For U1, from the part number you listed, the device has an open drain output which means it needs a pull up and is an active low out. __________________ Pay it forward.

10th August 2008, 02:44 AM	(permalink)
b_reagle	Thanks for the help kchriste. Is this the simpliest(cheapest) way of doing this?

10th August 2008, 02:55 AM	(permalink)
Mikebits	Did you read the follow on post, or just rubbing it in... __________________ Pay it forward.

10th August 2008, 03:02 AM	(permalink)
b_reagle	So Allvot, you say use a comparator instead of voltage reglator, or are you really just rubbing it in.LOL.

10th August 2008, 03:19 AM	(permalink)
b_reagle	Right voltage detector. Thanks again for your help.

10th August 2008, 03:33 AM	(permalink)
b_reagle	Good. That is a very cool part indeed. I never knew they existed. Now on the the next puzzle... Thanks again.